Mechanisms underlying the relationship between sun exposure and psoriasis

Psoriasis is a common chronic inflammatory skin disease.The nature of psoriasis remains unanswered,and its development is generally attributed to the interaction between environmental and genetic factors.Sunlight,as one of the environmental factors,is closely relevant to the occurence and sequelae of psoriasis.Ultraviolet radiation can induce apoptosis in keratinocytes and modulate abnormal immune responses,and in turn relieve clinical symptoms of psoriasis.Further more,ultraviolet radiation can accelerate the regeneration of keratinocytes by promoting skin to produce vitamin D.However,uhraviolet is the most common pollutant that causes the production of reactive oxygen species.If the production of reactive oxygen species exceeds the antioxidant capacity of the host,psoriasis may be induced,which may partly explain the pathogenesis of photosensitive psoriasis. Key words: Psoriasis ;  Sunlight ;  Apoptosis ;  Vitamin D